Australia has always had a reputation for astronomy. It is a great site low in the Southern hemisphere and there are lots of sparsely inhabited areas free from light and radio interference. Some of the first video from the Apollo 11 landing, for example, came in from “the dish” — a very large radio telescope down under. Australian hobbyists have formed a group, SpaceAusScope, where teams across Australia are building radio telescopes with the plan — which has been delayed by the pandemic — of collecting data and providing it for public analysis.
A secondary goal of the group is to provide better documentation for amateur radio telescope builders. So even if you don’t live in Australia, you might want to check out their website. It looks as thoughthe documentation will arrive in the future, but there is a very informative blog post from one team member about the helical antenna design most of the teams are using to eavesdrop on the hydrogen line.
[Geoff] had access to high dollar simulation tools and some test equipment, so he managed to build an antenna that has good performance and is easier to build than some other common antenna types. Receiving gear that would have been astronomically priced — no pun intended — a few years ago is now commonplace. If you ever thought about building a radio telescope, this might be the time to do it.